powerpc/pseries/iommu: Fix window size for direct mapping with pmem

As of today, if the DDW is big enough to fit (1 << MAX_PHYSMEM_BITS)
it's possible to use direct DMA mapping even with pmem region.

But, if that happens, the window size (len) is set to (MAX_PHYSMEM_BITS
- page_shift) instead of MAX_PHYSMEM_BITS, causing a pagesize times
smaller DDW to be created, being insufficient for correct usage.

Fix this so the correct window size is used in this case.

Fixes: bf6e2d562bbc4 ("powerpc/dma: Fallback to dma_ops when persistent memory present")
Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210420045404.438735-1-leobras.c@gmail.com

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 67c9953..5b3050f 100644 (file)
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -1252,7 +1252,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
        if (pmem_present) {
                if (query.largest_available_block >=
                    (1ULL << (MAX_PHYSMEM_BITS - page_shift)))
-                       len = MAX_PHYSMEM_BITS - page_shift;
+                       len = MAX_PHYSMEM_BITS;
                else
                        dev_info(&dev->dev, "Skipping ibm,pmemory");
        }